mysql - Sql Join taking a lot of time -
i tying execute query taking more 5 hours, data base size 20mb. code. here joining 11 tables reg_id. need columns distinct values. please guide me how rearrange query.
select * degree join diploma on degree.reg_id = diploma.reg_id join further_studies on diploma.reg_id = further_studies.reg_id join iti on further_studies.reg_id = iti.reg_id join personal_info on iti.reg_id = personal_info.reg_id join postgraduation on personal_info.reg_id = postgraduation.reg_id join puc on postgraduation.reg_id = puc.reg_id join skills on puc.reg_id = skills.reg_id join sslc on skills.reg_id = sslc.reg_id join license on sslc.reg_id = license.reg_id join passport on license.reg_id = passport.reg_id group fullname
please me if did mistake
this bit long comment.
the first problem query using select *
group fullname
. have zillions of columns in select
not in group by
. unless really, really, know doing (which doubt), wrong way write query.
your performance problem undoubtedly due cartesian products , lack of indexes. joining across different dimensions -- such skills , degrees. result product of possibilities. people, data size can grow , grow , grow.
and then, question is: have indexes on keys used in joins? performance, want such indexes.
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